The six kinds of simple machines Select a lesson
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Wheel and axel simple machine
Define a simple machine
types of machines
explain an inclined plane for children Explain a wedge simple machine
Explain a screw simple machine Explain a lever simple machine
Explain the wheel and axle simple machine What is a pulley simple machine
Terminology on simple machines
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The Lever simple machine



The Wedge (ramp)

A wedge is simply a triangular tool, often made of metal, wood, stone or plastic. It is thick on one end and tapers to a thin or sharp edge on the other end. Technically it is an inclined plane (or two inclined planes put together to form a triangle) that moves. A wedge may be attached to a handle to make it easier to use. Good examples of wedges are nails, knives, axes and your teeth!
exmaple of wedge simple machine

A wedge can be used in many ways:
uses of a wedge simple machineTo cut (knife)
uses of a wedge simple machineTo split (axe)
uses of a wedge simple machineTo tighten and to hold back (doorstopper)
uses of a wedge simple machineTo hold together (nail)
uses of a wedge simple machineTo scrape (blades on the snowplough or farm grader)

Wedges work by changing direction and force applied to it. Here is an illustration:Diagram of change in direction and force.wedge changing direction of the force

From the above, you will notice that the force applied to the thick end of the wedge overcomes the resistance of the wood. The force is directed downwards, but the wedge directs the force sideways as it drives into the wood.

double wedge and single wedegA wedge may be a single wedge or double wedge. Each does a slightly different job. An axe is a double wedge (see diagram above) and a chisel is a single wedge.

Trade-off
The longer and thinner a wedge is (sharper), the more work it does with little effort. If the wedge is shorter and has a wider angle at the tip, one needs more force to do the work.

The mechanical advantage of a wedge is higher when the wedge is longer with a thinner tip.

Wedges have been in use for millions of years. Earlier humans used wedges made of hard rocks and stones to hunt (like spears), cut and trim trees and carve stones. The concept of wedges is also used in jets and modern cars. You will notice that jets, fast cars, speed boats and trains have pointed noses. This helps them cut through the air (air acts as a resistance). This feature of pointed noses cutting through air is known as aerodynamics.

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pulley  simple machines




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